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12 February 1961

Venera 1, the first spacecraft to fly past Venus, was launched by the Soviet Union on February 12, 1961.

It was the second attempt by the Soviet Union to launch a craft toward Venus that month. Its sister ship, Venera-1VA No.1, failed to leave Earth orbit when launched on February 4, 1961 due to a problem with its upper stage.

The Soviets were still moving at a good speed in the Space Race and had been enjoying accomplishments with the Sputnik and Luna programs. The February 4 failure would not hold them back.

Venera 1 was launched using a Molniya carrier rocket from the Baikonur Cosmodrome. The spacecraft’s 11D33 engine was the first staged-combustion-cycle rocket engine, and also the first use of an ullage engine.

Three successful telemetry sessions were conducted that gathered solar-wind and cosmic-ray data near Earth, at the outer limit of Earth’s magnetosphere, and at a distance of 1,900,000 km. After discovering the solar wind with Luna 2, Venera 1 provided the first verification that this plasma was uniformly present in deep space.

Unfortunately, just a week after making this discovery, Venera 1’s next scheduled telemetry session failed to occur and communication was lost. It is believed that the failure was due to the overheating of a solar-direction sensor.

On May 19 and 20, 1961, Venera 1 passed within 100,000 km of Venus. With the help of a British radio telescope, some weak signals from Venera 1 may have been detected in June but, overall, communication with the spacecraft was considered ended and any data transmitted at that point is considered lost.